When a struct_ops named xxx_ops was registered by a module, and it will be used in both built-in modules and the module itself, so that the btf_type of xxx_ops will be present in btf_vmlinux instead of in btf_mod, which means that the btf_type of bpf_struct_ops_xxx_ops and xxx_ops will not be in the same btf. Here are four possible case: +--------+-------------+-------------+---------------------------------+ | | st_opx_xxx | xxx | | +--------+-------------+-------------+---------------------------------+ | case 0 | btf_vmlinux | bft_vmlinux | be used and reg only in vmlinux | +--------+-------------+-------------+---------------------------------+ | case 1 | btf_vmlinux | bpf_mod | INVALID | +--------+-------------+-------------+---------------------------------+ | case 2 | btf_mod | btf_vmlinux | reg in mod but be used both in | | | | | vmlinux and mod. | +--------+-------------+-------------+---------------------------------+ | case 3 | btf_mod | btf_mod | be used and reg only in mod | +--------+-------------+-------------+---------------------------------+ At present, cases 0, 1, and 3 can be correctly identified, because st_ops_xxx is searched from the same btf with xxx. In order to handle case 2 correctly without affecting other cases, we cannot simply change the search method for st_ops_xxx from find_btf_by_prefix_kind() to find_ksym_btf_id(), because in this way, case 1 will not be recognized anymore. To address this issue, if st_ops_xxx cannot be found in the btf with xxx and mod_btf does not exist, do find_ksym_btf_id() again to avoid such issue. Fixes: 590a00888250 ("bpf: libbpf: Add STRUCT_OPS support") Signed-off-by: D. Wythe <alibuda@xxxxxxxxxxxxxxxxx> --- tools/lib/bpf/libbpf.c | 34 +++++++++++++++++++++++++++++++--- 1 file changed, 31 insertions(+), 3 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 66173ddb5a2d..046feab4ec36 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -994,6 +994,27 @@ static int find_ksym_btf_id(struct bpf_object *obj, const char *ksym_name, static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix, const char *name, __u32 kind); +static int +find_ksym_btf_id_by_prefix_kind(struct bpf_object *obj, const char *prefix, + const char *name, + __u16 kind, struct btf **res_btf, + struct module_btf **res_mod_btf) +{ + char btf_type_name[128]; + int ret; + + ret = snprintf(btf_type_name, sizeof(btf_type_name), + "%s%s", prefix, name); + /* snprintf returns the number of characters written excluding the + * terminating null. So, if >= BTF_MAX_NAME_SIZE are written, it + * indicates truncation. + */ + if (ret < 0 || ret >= sizeof(btf_type_name)) + return -ENAMETOOLONG; + + return find_ksym_btf_id(obj, btf_type_name, kind, res_btf, res_mod_btf); +} + static int find_struct_ops_kern_types(struct bpf_object *obj, const char *tname_raw, struct module_btf **mod_btf, @@ -1028,9 +1049,16 @@ find_struct_ops_kern_types(struct bpf_object *obj, const char *tname_raw, kern_vtype_id = find_btf_by_prefix_kind(btf, STRUCT_OPS_VALUE_PREFIX, tname, BTF_KIND_STRUCT); if (kern_vtype_id < 0) { - pr_warn("struct_ops init_kern: struct %s%s is not found in kernel BTF\n", - STRUCT_OPS_VALUE_PREFIX, tname); - return kern_vtype_id; + if (kern_vtype_id == -ENOENT && !*mod_btf) + kern_vtype_id = + find_ksym_btf_id_by_prefix_kind(obj, STRUCT_OPS_VALUE_PREFIX, + tname, BTF_KIND_STRUCT, &btf, + mod_btf); + if (kern_vtype_id < 0) { + pr_warn("struct_ops init_kern: struct %s%s is not found in kernel BTF\n", + STRUCT_OPS_VALUE_PREFIX, tname); + return kern_vtype_id; + } } kern_vtype = btf__type_by_id(btf, kern_vtype_id); -- 2.45.0